Also, I doubt that a shim for such a small difference would be available. It would have to be 0.1mm in thickness which is probably slightly thinner than tin foil!
In short, I wouldn't risk doing it if I were you. Far easier to buy a 27.2 post to fit a 27.2 frame. (a 27.0 post for a 27.0 frame however is a bit more difficult to find these days).